Low NOX gas combustion systems

Abstract

Air pollution from combustion of air/gas mixtures is reduced effectively and reliably at a porous burner providing flames with a downstream reaction zone where the ignition of the air/gas mixture initiates. The porous burner is loaded with the air/gas mixture sufficiently, such as at from 1000 to 2500 kWm -2 or 2200 to 5500 Btu/sqin-hr, to locate the downstream reaction zone at a downstream surface of the porous burner, while the air/gas mixture is provided with sufficient excess air, such as more than a quarter of excess air, for the flames to burn blue. In a typical combustion of that air/gas mixture, less than 20 ppm of NO x are produced. A related method loads the porous burner with the air/gas mixture at from 1000 to 2000 kWm -2 or 2200 to 4400 Btu/sqin-hr, while providing that air/gas mixture with more than about forty-five percent of excess air for the flames to burn blue. That combustion of the air/gas mixture including its excess air produces less than 10 ppm of NO x .

I claim: 
     
       1. A method of operating a porous burner with an air/gas mixture, comprising in combination: igniting said air/gas mixture at said porous burner to produce flames with a downstream reaction zone;   loading said porous burner with said air/gas mixture sufficiently by force-feeding to locate said downstream reaction zone at a downstream surface of said porous burner; and   providing said air/gas mixture with sufficient excess air for said flames to burn blue in a combustion of said air/gas mixture including said excess air producing less than 20 ppm of NO x .   
     
     
       2. A method as in claim 1, wherein: said air/gas mixture is provided with more than a quarter of excess air.   
     
     
       3. A method as in claim 1, including: intimately admixing the gas and the air in said air/gas mixture by forcing said air/gas mixture including said excess air through a flow impedance ahead of said porous burner.   
     
     
       4. A method as in claim 3, wherein: said air/gas mixture is provided with more than a quarter of excess air.   
     
     
       5. A method as in claim 1, including: intimately admixing the gas and the air in said air/gas mixture by forcing said air/gas mixture including said excess air through a bent path ahead of said porous burner.   
     
     
       6. A method as in claim 5, wherein: said air/gas mixture is provided with more than a quarter of excess air.   
     
     
       7. A method as in claim 1, wherein: the gas and the air in said air/gas mixture are intimately admixed by feeding said air/gas mixture including said excess air through a blower and force-feeding air/gas mixture including said excess air to said porous burner with said blower.   
     
     
       8. A method as in claim 7, wherein: said air/gas mixture is provided with more than a quarter of excess air.   
     
     
       9. A method of operating a porous burner with an air/gas mixture, comprising in combination: igniting said air/gas mixture at said porous burner to produce flames with a downstream reaction zone;   loading said porous burner with said air/gas mixture at from 1000 to 2500 kWm -2  or 2200 to 5500 Btu/sqin-hr; by force-feeding and   providing said air/gas mixture with sufficient excess air for said flames to burn blue in a combustion of said air/gas mixture including said excess air producing less than 20 ppm of NO x .   
     
     
       10. A method as in claim 9, wherein: said air/gas mixture is provided with more than a quarter of excess air.   
     
     
       11. A method as in claim 9, including: intimately admixing the gas and the air in said air/gas mixture by forcing said air/gas mixture including said excess air through a flow impedance ahead of said porous burner.   
     
     
       12. A method as in claim 11, wherein: said air/gas mixture is provided with more than a quarter of excess air.   
     
     
       13. A method as in claim 9, including: intimately admixing the gas and the air in said air/gas mixture by forcing said air/gas mixture including said excess air through a bent path ahead of said porous burner.   
     
     
       14. A method as in claim 13, wherein: said air/gas mixture is provided with more than a quarter of excess air.   
     
     
       15. A method as in claim 9, wherein: the gas and the air in said air/gas mixture are intimately admixed by feeding said air/gas mixture including said excess air through a blower and force-feeding air/gas mixture including said excess air to said porous burner with said blower.   
     
     
       16. A method as in claim 15, wherein: said air/gas mixture is provided with more than a quarter of excess air.   
     
     
       17. A method of operating a porous burner with an air/gas mixture, comprising in combination: igniting said air/gas mixture at said porous burner to produce flames with a downstream reaction zone;   loading said porous burner with said air/gas mixture at from 1000 to 2000 kWm -2  or 2200 to 4400 Btu/sqin-hr; by force-feeding and   providing said air/gas mixture with more than about forty-five percent of excess air for said flames to burn blue in a combustion of said air/gas mixture including said excess air producing less than 10 ppm of NO x .   
     
     
       18. A method as in claim 17, including: intimately admixing the gas and the air in said air/gas mixture by forcing said air/gas mixture including said excess air through a flow impedance ahead of said porous burner.   
     
     
       19. A method as in claim 17, including: intimately admixing the gas and the air in said air/gas mixture by forcing said air/gas mixture including said excess air through a bent path ahead of said porous burner.   
     
     
       20. A method as in claim 17, wherein: the gas and the air in said air/gas mixture are intimately admixed by feeding said air/gas mixture including said excess air through a blower and force-feeding air/gas mixture including said excess air to said porous burner with said blower.